Tick the log data box on the graph or data object, not the Event Manager, and send the records to the second card slot, CF2. Slot 1 is a boot slot: with a card present at power-up the panel looks there for its program. Start at one sample per minute, size the card by years of margin, and power down before you pull it.
Data logging to a CF card starts at the graph or data object, not at the Event Manager. Open the object whose values you want on the card, tick its log data box, and pick the memory location in the same settings. Send the records to CF2, the second card slot, and leave CF1 to its boot job. Start at one record per minute: at that pace a small card holds years of history, and the only decisions that need care are the slot and a safe removal. The steps below cover the checkbox, the slot, the interval, and pulling the card without losing records.
What you need
- The programming software with the project open, and the panel it runs on
- A CF card dedicated to logging, which lives in slot 2, CF2, and stays there
- A decision on slot 1: keep the program card in CF1, or leave the slot empty if the project runs from the panel's own memory
- One value you can change on demand from the PLC side, to check that records are being written
- For occurrence records, an Alarm or Message already in the project
Tick the log data box on the object
- In the programming software, open the graph or data object that displays the values you want on the card.
- On that object's Option tab, find the More Info link, then look just above it and tick the log data box.
- Choose the memory location in the same settings and select CF2.
- Set how often each record is written. One record per minute is a workable start for process values; the figure to beat is the fastest change you need to reconstruct later.
- Save the project and transfer it to the panel with your normal transfer process.
The trap is the More Info link. It explains the Event Manager, which reacts to events and has no control that writes sampled values, so that route never starts this log. The box you want sits above the link, on the object's own settings.
For what a panel can hold for later retrieval in the first place, see Can an HMI panel store PLC data for later retrieval?.
Keep the log off CF1
CF1 is the boot slot. With a card present in slot 1 at power-up, the panel looks there for its program, and a card that holds only log files can change how the panel starts or leave it without the project you expect. Keep slot 1 for the program card, or leave it empty when the project runs from the panel's memory, and give the log CF2. The panel then starts from one slot and writes to the other, and pulling the log card never touches what the panel boots from. If a panel ever comes up without its project after a power cycle, check the storage arrangement first: HMI panel loses its project after a power cycle.
Record an occurrence as an Alarm or a Message
Sampled values go in the data log. Something that happens once, a fault or a batch start, cannot be logged as data; configure it as an Alarm or a Message and set where records are stored in Panel Manager, under Data Storage. To keep the record without showing anything at the panel, uncheck Show in AlarmHistory, Confirmation, and Display on the alarm. Do that only for records no operator has to act on: those three checkboxes also remove the on-screen message and the acknowledgment step.
Example: card size at one record per minute
Take a log of four values, one timestamped line of about 40 bytes, written once per minute.
- Records per day: 60 per hour x 24 hours = 1,440 records
- Bytes per day: 1,440 x 40 bytes = 57,600 bytes, about 57.6 KB
- Bytes per year: 57.6 KB x 365 days = about 21 MB
A 512 MB card holds about 24 years of that log. Cut the interval to one record every 10 seconds and the same line grows to 8,640 records per day and about 126 MB per year, still a fraction of a small card. At these rates capacity never forces a decision, so pick the interval for the process, not for the card. A slower pace is often the right call, as in HMI data logging: 10-minute interval for switch states. Plan card swaps around archiving, never around space.
Pull the card safely
Power the panel down before removing the card, unless your project exposes the panel's eject control. This panel family carries internal status and control values for card free space and for eject, and those values can stop the transfer for a safe removal. Where your software exposes them, operate the eject and wait for the safe indication before the card comes out; where nothing shows card status, switch the panel off and swap with the power down. Do not use the sample interval as the test: a write can sit in a buffer between two records even while the record count looks current. Label the cards and rotate them on a schedule; the swap routine itself is in Proprietary HMI CompactFlash card replacement: the safe swap.
How to check it worked
Run the panel with both cards in place, force the logged value to change from the PLC side, and wait through three sample intervals, about three minutes at a one-minute pace. Remove the log card by the safe procedure above, read it on a PC, and look for one record per minute at the timestamps you forced. Seat both cards again, power the panel off and on once, and make sure it starts its project as before. If records are missing, check in this order: the log data box on the object, the memory location, the interval, then whether you are reading the slot the log actually points to.
Recommendation: Tick the log data box on the graph or data object, choose CF2 as the memory location, and leave CF1 as the boot card or empty. Start at one record per minute and tune the interval to the fastest change you need to reconstruct. Record occurrences as Alarms or Messages with the destination set in Panel Manager under Data Storage, and power down before pulling the card unless your project operates the panel's eject control.
Questions
Why does the log end a record or two before I switched the panel off?
The last writes were still held in the panel's write buffer when power went away, so the card ends at the last completed record and the tail is lost. That is normal after a plain power-off, and it is the cost the eject control exists to avoid: stop the transfer, then remove, and the card ends exactly where you stopped it.
What does the panel look for on a card in slot 1 at power-up?
Its startup project. In this panel family the program stored on a CF card is kept as a STARTUP STORAGE (*.EAS) file, and the panel checks slot 1 for it whenever a card is present there at boot. That is why a card holding only logs in slot 1 can change how the panel starts. Keep slot 1 for the program card, or empty when the project runs from the panel's own memory.
Does logging keep working after a panel power cycle?
Yes. The log data setting and the memory location are saved in the project, so after a power cycle the panel resumes writing on its own, with no re-transfer, as long as the cards are back in their slots: program card in CF1 or slot 1 empty, log card in CF2. If the panel instead comes up without its project, the storage arrangement, not the logging settings, is what to fix.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.